[Mesa-users] Core mass,center_h1 going up on the MS

[Pablo Marchant]

Dear Giovanni,

from checking your inlist I see that you are using the Schwarzschild
criterion for convection (which is the default, Ledoux is set with the
option use_Ledoux_criterion) without overshooting. This is know to case
issues, I would recommend including some core overshooting or using the
convective pre-mixing option that does a better job setting the convective
boundary (this can be turned on with do_conv_premix=.true., see Paxton et
al. 2019 section 5 for details).

Cheers

On Tue, Jun 2, 2020 at 6:48 PM GM Mirouh via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Dear all,
>
> I am trying to compute models of massive stars along the main sequence,
> saving models along the way: to do so, I use xa_central_lower_limit to
> stop, but I have noticed a weird behaviour.
>
> At some point during the main sequence evolution of a 30Msun star, at
> model_number=3930, the convective core mass goes from 1.22 to 1.67Msun
> and the core mass fraction goes from 0.311 to 0.368. The core then
> shrinks to 1.00Msun at the next timestep, and the core abundance seems
> to evolve more or less normally. Setting dH_decreases_only to true
> changes nothing to this, nor does changing varcontrol, but I have
> noticed that the amplitude of the bump in center_h1 depends on the
> timestep controls I use (but not in a simple way)...
>
> I do not think this is physical, and even it were, I am worried about
> such a large jump in center_h1 and how it may bias my use of
> xa_central_lower_limit (if I set it to 0.35, then I will spot the first
> passage, but what about the second? what about the age, for models at
> lower values?).
> Do you have any idea how I could avoid this bug (if it's a bug) or
> smooth this variation in core mass (if it's physical)? I have noticed
> this behaviour for other masses, and can provide more examples if need be.
>
> I use mesa version 11701. I have attached a minimal example inlist and
> part of my history file where the thing happens.
> Thanks a lot,
> Best.
>
> --
> Giovanni.
>
> _______________________________________________
> mesa-users at lists.mesastar.org
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>
>

-- 
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
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